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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Alexey Gladkov <gladkov.alexey@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Alexey Gladkov <legion@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Kees Cook <keescook@chromium.org>
References: <cover.1613550081.git.gladkov.alexey@gmail.com>
Date:   Mon, 22 Feb 2021 09:44:40 -0600
In-Reply-To: <cover.1613550081.git.gladkov.alexey@gmail.com> (Alexey Gladkov's
        message of "Wed, 17 Feb 2021 09:21:40 +0100")
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Subject: Re: [RESEND PATCH v4 0/3] proc: Relax check of mount visibility
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Alexey Gladkov <gladkov.alexey@gmail.com> writes:

> If only the dynamic part of procfs is mounted (subset=pid), then there is no
> need to check if procfs is fully visible to the user in the new user
> namespace.


A couple of things.

1) Allowing the mount should come in the last patch.  So we don't have a
bisect hazard.

2) We should document that we still require a mount of proc to match on
atime and readonly mount attributes.

3) If we can find a way to safely not require a previous mount of proc
this will be much more valuable.

Eric